I'm going to build a A frame gantry for use in the workshop. It won't need to lift more than 1 tonne so nothing too sturdy. I already have a suitable length of beam for the top rail but need to buy the steel to make the two A frames. Does anyone have the knowledge to size the steel ? The frames will be about 2.5 m tall and the base about 1250 wide which gives them an included angle of about 30 degrees. I was thinking of using a box section of perhaps 6.0 mm thick . Ideally no larger than 80 x 80 mm as this would suit the junctions to the beam etc. Smaller would be better for sake of cost and weight. Any ideas? The span for the beam is only 2.4 metres and I don't want any diagonal braces from the beam as I need the carriage to be able to go to the ends for parking. I would add that I've done some considerable viewing of photos of frames on the net but the construction does vary considerably and of course you can't see the section wall thickness.